Screen plate



NOV- 10, 1942- G. c. BREwsTl-:R 2,301-,514

EEEEEEEEE TE Nov. 10, 1942.

G. C. BREWSTER SCREEN PLATE Filed Oct. 5, 1939 2 Sheets-Sheet 2 Patented Nov. 10, 1942 UNITED STATES FATENT OFFICE SCREEN PLATE Grover C. Brewster, Shelton, Wash.

Application October 5, 1939, Serial No. 298,122

1 Claim.

This invention relates to an improved screen plate for paper making machines.

As is well known, the slots, in plates of this character, are subject to wear and corrosion which, under present practice, usually results in discarding the entire plate, even though only a few slots may be affected, as the efii'ciency of the plate, as a whole, is dependent upon the preciseness an'd uniformity of the slots.

An object of -the present invention, therefore, is to provide a plate which, in original construction, will embody sufficient reserve metal, at the proper points, available to permit closing of the slots, as by a process -of rolling to which the plate may be subjected, and re-cutting of the slots, thus to restore the plate to its initial efficiency.

A further object of the invention is to provide a plate wherein the reserve metal will be bulked to form convex crowns on the bars of the plate between the slots.

Still another object i to provide a plate Whereln flats will be provided at opposite sides of the mouth of each slot throughout the length thereof, a pair of fiats thus lying at opposite sides of each slot between an adjacent pair of crowns.

A further object of the invention is to gain a double advantage through the provision of reserve metal for closing the slots, namely, first, to

initially shape this reserve metal into crowns on Other and incidental objects of the invention will appear during the course of the following description and in the drawings:

Figure 1 is a fragmentary top plan view of a screen plate Constructed in accordance With the present invention.

Figure 2 is a fragmentary longitudinal section on the line 2-2 of Figure 1.

Figure 3 is a fragmentary transverse section on the line 3-3 of Figure 1..

Figure 4 is a detail sectional perspective view,

greatly enlarged to better show structural detali. Figure 5 is an inverted fragmentary plan view showing a so-called Bird or rotary plate,

Figure 6 is a fragmentary section on the line 6-6 of Figure 5.

Figure 7 is a fragmentary section on the line 1-1 of Figure 5, bringing out the curvature.

As Will be appreciated, screen plates are rectangular in over-all sha-pe and flat plates usually embody two or more longitudinal stripes of transverse slots while curved plates may embody four or more such stripes of slots. It has been deeined sufiicient, in the present instance, to show a typical portion of each plate, as a further showing would be unnecessary to an understanding of the invention for those skilled in the art.

Figures 1, 2, 3 and 4 of the drawings show a flat plate. The plate includes side panels I, end panele H and a center panel [2. At each side of the center panel is a longitudinal stripe of transverse slots, a typical few of which are shown and will be described. The drawings are on an exaggerated scale to better show structure. Preferably, the major thickness of the plate is close to five sixteenths of an inch, length, say for a typical instance, forty-three inches, and width, ten and three quarter inches. These dimensions may be unnecessary, but are given as illustra'tive although, of course, I do not wish to be limited thereto.

The slots mentioned are indicated at I and, as best brought out in Figure 4 of the drawings, are Wedge shaped or widened toward their discharge limits. These slots define a series of bars I4 separated by the slots. At one side of the plate, the metal is bulked to provide a convex Crown I 5 for each bar and sharply defining these crowns are fiats or lips l which extend from end to end of the slots. As will be perceived, a pair of flats is disposed at opposite sides of each slot, the

combined surface of each pair of flats providing a drainage area contiguous to the mouth of each slot. One of the purposes of this construction is to feed the stock and water, by the convexity of the crowns, to the slots, thus increasing the capacity of the plate. Another purpose is to provide for relatively still drainage areas between the crowns so as to prevent cl'ogging or at least retard clogging when the stock is thick,

The foregoing may perhaps be made a little more clear. It will be assumed that stock and water are flowing over the plate in its usual inclined position. As will be grasped, the curvature of the crowns I5 will act to create a rush of the liquid pulp tending to cause said pulp to flow over and past the mouth of each slot. In the present construction, this tendency is counteracted by the presence of the flats IE. For instance, assume a pair of crowns I and an intervening pair of fiats IS. The crowns provide dams and the flats provide relatively still pools for the stock so that, independently of the gravitational flow of the bulk of stock passing over the screen, each pool, as outlined, provides a relatively still Volume tending to arrest the surface flow and cause the material to ficw into and through the slots.

The dimensions involved are necessarily small. For instance, the crowns are preferably about .0l2" and the slots, including the crowns, about five thirty seconds of an inch. This leaves about five thirty seconds of an inch below the slots. In the present construction, the milling. is carried about one quarter inch beyond each end of the mouth of each slot, as shown. Flatv screen plates, under different screening Conditions, wear at times, more at the ends of the slots than at the middle area and by folming the crowns l to extend approximately a quarter inch beyond the ends of the slots, metal is provicled at these Vital points to permit re-closingof the slots andV re-cutting, as shall presently appear.

Formed in the lower sideV of the plate tol communicate with the slots l3 are inverted, truncated V-shaped channels l each defining a pair of lateral flats orshoulders 58 at the discharge slit of each slot. Clearanceis thus providedL so as to retard fouling of the stock at the discharge slits and, due to the downward widening of the slots l3, in conjuncticn with the clearance provided by said flats, it has been found that the capacity of the plate is materially increased. II'he channels il' define ribs ES at the lower edges of the bars ili, these ribs being of inverted truncated pyramidal shape in cross section. The bars are thus strengthened and reinforced by said ribs so that the accurate parallelism of the bars will be preserved intact.

Assuming now that it is desired to recover the plate, when worn, the plate is suitably rolled transversely or, in other words, in a direction longitudinally of the bars lil. The crowns l5 will thus be fiattened and the reserve metal therein utilized to spread the bars and close the slots l. The slots may then be re-cut to accurate definition. The number of slots i and bars Ed per longitudinal inch of the plate will, of course, be determined by the exact transverse diinensions of the bars.

It has been found that by providing the bars ill with the crowns lb of say .012, more or less, as previously noted, the life of the plate is bars 2! practically doubled. On the average, not more than half of the reserve metal of the several crowns will be required for a usual re-closing and re-cutting job and the plate Will maintain its Width at all times while, also, the bars will remain straight with no tension such as might sprng them out of place.

In Figures 5, 6 and 7 of the drawings, I have shown a curved screen plate embodying the present improvements. It would appear superfluous to describe the panels and body Structure of the curved plate.

Coming now to detail Structure, the plate includes stripes of V-slots 28 defining intervening having convex crowns 22, truncated pyramidalribs 23, truncated V-channels 24, and fiats 25, as described in connection with the prior embodment of the invention. Reserve metal is thuspresent in the crowns 22 to perrnit recovery of* the plate, when worn, as previously described.

Having thus described my in-vention, I claim:

A unitary metallic screen plate of uniform thickness and having integral structural parts fashioned from the thiclcness of the plate and embodying a, plurality of parallel bars each including convex crown at the upper surface of the bar, fiat lateral lips at the upper margins of the bar delimiting the crown, flat sides slightly converging downwardly, fiat lateral shoulders opposite said lips and parallel thereto at the lower limits of said sides, and truncated. V-shaped ribs tapering olownwardlyV from the inner angles of said shoulders, the sides being defined by downwardly widened parallel slots of Uniform depth separating the bars whereby each slot is fianlzed at its mouth by a pair .of said lips to provide a flat-bottomed catch basin between eachpair of crowns for arresting the current of material flowing vover the plate and is fianked at its exit with a pair of said shoulders to provide lateral- Clea-rance for said material, the major height of each crown being disposed within bthe lines of the plate and appreciably less than the depth of each slot and the height of any one crown combined With the depth of any one slot being` Sub.- stantially halfy the thickness of said plate, the bars being of unitary integral construction integral with theplate and the crowns being longer than said slots wherebyv the plate may be rolled to fiatten said crowns and crowd the metal of the bars to laterally enlarge said bars and close said slots from end to endfor recutting.

GROVER C. BREXVS'IER. 

